Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753006Ab0KZBZo (ORCPT ); Thu, 25 Nov 2010 20:25:44 -0500 Received: from gir.skynet.ie ([193.1.99.77]:37843 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752470Ab0KZBZn (ORCPT ); Thu, 25 Nov 2010 20:25:43 -0500 Date: Fri, 26 Nov 2010 01:25:27 +0000 From: Mel Gorman To: Shaohua Li Cc: Simon Kirby , KOSAKI Motohiro , "linux-mm@kvack.org" , linux-kernel , Dave Hansen Subject: Re: Free memory never fully used, swapping Message-ID: <20101126012527.GI26037@csn.ul.ie> References: <20101115195246.GB17387@hostway.ca> <20101122154419.ee0e09d2.akpm@linux-foundation.org> <1290501331.2390.7023.camel@nimitz> <20101124084652.GC25170@hostway.ca> <1290647274.12777.3.camel@sli10-conroe> <20101125090328.GB14180@hostway.ca> <20101125161238.GD26037@csn.ul.ie> <1290733556.12777.5.camel@sli10-conroe> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1290733556.12777.5.camel@sli10-conroe> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3216 Lines: 75 On Fri, Nov 26, 2010 at 09:05:56AM +0800, Shaohua Li wrote: > > @@ -2168,6 +2180,7 @@ static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining) > > static unsigned long balance_pgdat(pg_data_t *pgdat, int order) > > { > > int all_zones_ok; > > + int any_zone_ok; > > int priority; > > int i; > > unsigned long total_scanned; > > @@ -2201,6 +2214,7 @@ loop_again: > > disable_swap_token(); > > > > all_zones_ok = 1; > > + any_zone_ok = 0; > > > > /* > > * Scan in the highmem->dma direction for the highest > > @@ -2310,10 +2324,12 @@ loop_again: > > * spectulatively avoid congestion waits > > */ > > zone_clear_flag(zone, ZONE_CONGESTED); > > + if (i <= pgdat->high_zoneidx) > > + any_zone_ok = 1; > > } > > > > } > > - if (all_zones_ok) > > + if (all_zones_ok || (order && any_zone_ok)) > > break; /* kswapd: all done */ > > /* > > * OK, kswapd is getting into trouble. Take a nap, then take > > @@ -2336,7 +2352,7 @@ loop_again: > > break; > > } > > out: > > - if (!all_zones_ok) { > > + if (!(all_zones_ok || (order && any_zone_ok))) { > > cond_resched(); > > > > try_to_freeze(); > > @@ -2361,7 +2377,13 @@ out: > > goto loop_again; > > } > > > > - return sc.nr_reclaimed; > > + /* > > + * Return the order we were reclaiming at so sleeping_prematurely() > > + * makes a decision on the order we were last reclaiming at. However, > > + * if another caller entered the allocator slow path while kswapd > > + * was awake, order will remain at the higher level > > + */ > > + return order; > > } > This seems always fail. because you have the protect in the kswapd side, > but no in the page allocation side. so every time a high order > allocation occurs, the protect breaks and kswapd keeps running. > I don't understand your question. sc.nr_reclaimed was being unused. The point of returning order was to tell kswapd that "the order you were reclaiming at may or may not be still valid, make your decisions on the order I am currently reclaiming at". The key here is if that multiple allocation requests come in for higher orders, kswapd will get reworken multiple times. Unless it gets rewoken multiple times, kswapd is willing to go back to sleep to avoid reclaiming an excessive number of pages. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/